Right now atkobject defines these abstract methods:

  /*
   * Specifies a function to be called when a property changes value
   */
guint (* connect_property_change_handler) (AtkObject *accessible,
                                           AtkPropertyChangeHandler *handler);
  /*
   * Removes a property change handler which was specified using
   * connect_property_change_handler
   */
void (* remove_property_change_handler)     (AtkObject *accessible,
                                             guint handler_id);

IMHO, those should be deprecated:

* This is basically a wrapper to "property-change" signal.
* It is only implemented by atkobject. I didn't find any implementation on gtk or clutter.
* It is no used by anyone relevant. Ie: at-spi2-atk add a global listener to "property-change"
* I only found a place using this: tests on the old gail repository. 

Although we are already thinking about how useful is property-change signal (bug 644747), those methods can be deprecated maintaining property-change.